The invention relates to surface preparation, cleaning, rinsing and drying of workpieces, such as semiconductor wafers, flat panel displays, rigid disk or optical media, thin film heads, or other workpieces formed from a substrate on which microelectronic circuits, data storage elements or layers, or micro-mechanical elements may be formed. These and similar articles are collectively referred to here as a xe2x80x9cwaferxe2x80x9d or xe2x80x9cworkpiecexe2x80x9d.
The semiconductor manufacturing industry is constantly seeking to improve the processes used to manufacture microelectronic circuits and components, such as the manufacture of integrated circuits from wafers. The objectives of many of these improved processes are decreasing the amount of time required to process a wafer to form the desired integrated circuits; increasing the yield of usable integrated circuits per wafer by, for example, decreasing contamination of the wafer during processing; reducing the number of steps required to create the desired integrated circuits; and reducing the costs of manufacture.
In the processing of wafers, it is often necessary to subject one or more sides of the wafer to a fluid in either liquid, vapor or gaseous form. Such fluids are used to, for example, etch the wafer surface, clean the wafer surface, dry the wafer surface, passivate the wafer surface, deposit films on the wafer surface, etc. Controlling how the processing fluids are applied to the wafer surfaces, is often important to the success of the processing operations.
Various machines and methods have been used for carrying out these manufacturing processes. However, existing machines have several disadvantages. These disadvantages include relatively large consumption of process chemicals and water. This consumption of process chemicals increases manufacturing costs, which ultimately increases the cost of the final product, such as e.g., computers, cell phones, and virtually all types of consumer, industrial, commercial and military electronic products. In addition, many process chemicals are toxic and require special handling, storage, and disposal methods. These can be costly and difficult, but are necessary for health, safety and environmental reasons. Consequently, reducing consumption of process chemicals has many advantages.
Reducing consumption of water is also beneficial. In many areas, water is becoming increasingly scarce. Due to population growth, there is greater competition for water. Disposing of waste water in environmentally friendly ways has also often become more difficult or costly. Accordingly, reducing water consumption in the manufacturing process is also important.
Generally, the microelectronic circuits now used in virtually all electronic products are manufactured from flat round disks or wafers made of a semiconductor material, such as silicon. The side or suface of the wafer having the microelectronic circuits is called the device side. The other side is often referred to as the back or bottom side of the wafer. In a fab or manufacturing facility, special machines or robots and techniques are used in moving, handling and storing wafers, to maintain the wafers in an ultra-clean environment. With these techniques, the wafers are uniformly delivered to each process machine in a device side up orientation. This works well for the majority of process steps. However, for some process steps, receiving the wafer in a device side down orientation would be desirable. For example, if the device side is to be processed with a liquid, having the device side down helps to remove the liquid via gravity, a feature not available with device side up processing. While flipping the wafer over from a device side up to a device side down orientation may conceptually be a simple event, in practice it presents substantial engineering challenges. Initially, the wafer typically can only be picked up at the edges, and no other part of the wafer may be touched (to reduce contamination). In addition, the wafer must of course be securely gripped or held before it is flipped over. The flipping over or inverting step must be performed in a small amount of space, since space is scarce and costly in the clean room areas of fabrication facilities. Moreover, the flipping step must be performed quickly, to avoid slowing manufacturing operations, and with a minimum of movements or transfers of the workpiece.
In many process manufacturing steps, the process chemicals used should be applied evenly onto the wafers, to avoid having too much or too little etching, film removal, etc. Existing machines often are not able to sufficiently uniformly apply process chemicals. This can result in lower yields. Moreover, many existing machines try to compensate for variations in applying process chemicals by using larger amounts of process chemicals. This inefficient use of process chemicals leads to the disadvantages described above. Accordingly, improved machines and methods which provide improved yield, consume less process chemicals and water, provide more versatility, and offer better results in performing manufacturing operations, are needed.
Machines and methods have now been invented which overcome the disadvantages described above. In one design, the machine includes a workpiece housing having a processing chamber. Processing fluids are distributed across the surface of the workpiece in the processing chamber, by centrifugal force.
In a first aspect, the machine has a head having a first rotor and a second rotor engageable with the first rotor to hold a workpiece between them. The second rotor preferably has an open central area, to expose a bottom surface of the workpiece. The exposed bottom surface of the workpiece is contacted with a liquid via fixed or moving spray nozzles or liquid applicators, or by contact with a bath of liquid. With this design, consumption of process chemicals and water is dramatically reduced. Distribution of the process chemicals on the workpiece is controlled by the rotors, resulting in more uniform and efficient processing. Multiple process steps can also be performed in the machine, reducing the potential of loss of the workpiece due to contamination, and expediting manufacturing steps.
In a second and separate aspect, the first and second rotors each have a chamber access opening. The first and second rotors are moveable relative to each other to at least partially align the openings, for loading and unloading a workpiece. The first and second rotors are also moveable relative to each other, so that the access openings are not aligned during processing of the workpiece. Preferably, the head includes at least one actuator for moving at least one of the rotors in a direction parallel to the spin axis of the rotors. This design allows workpieces to be more quickly and easily loaded into and unloaded from the machine.
In a third aspect, the head is attached to a support arm on a head lifter, for vertically moving the head towards and away from a base having a liquid source for applying liquid to a bottom surface of the workpiece. The liquid source may be a bowl containing the liquid, optionally including a sonic energy source, such as a mega sonic transducer. This design provides a versatile machine which can perform more types of processing steps, including flipping the workpiece to perform device side down processing.
In a fourth and separate aspect, in a method for processing a workpiece, the workpiece is moved horizontally into a process head. The head and workpiece are inverted and lowered down towards a liquid source which provides a liquid onto the bottom surface of the workpiece. Liquid is applied to the bottom surface of the workpiece, by direct contact with a bath of liquid, or via a liquid outlet, by spraying, or by immersion. The workpiece is rotated during or after liquid is applied to the bottom surface of the workpiece. A same, or a different liquid, or a gas or vapor, is optionally introduced to the top surface of the workpiece. This method provides a variety of process steps, with less process chemical and water consumption. It also requires less need for movement of the workpiece, reducing manufacturing time and space requirements.
Accordingly, it is an object of the invention to provide improved methods and apparatus for processing a workpiece. The invention resides as well in subcombinations of the steps and features described. The features described and illustrated in connection with one embodiment may or course be used in other embodiments as well.